Method and Apparatus for Encoding Envelopes of Harmonic Signals and Method and Apparatus for Decoding Envelopes of Harmonic Signals

1. A method of encoding an audio signal, the method comprising: performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals, wherein the harmonic parameters comprise amplitudes of the harmonic signals; performing a time-frequency transformation by correlating the amplitudes of the harmonic signals included in the harmonic parameters to signals in a time domain instead of signals in a frequency domain, and applying a time-frequency transformation operation to the amplitudes in the time domain to generate time-frequency transformed values in the frequency domain; and encoding the time-frequency transformed values.

2. The method of claim 1 , wherein the performing the time-frequency transformation comprises: numbering the harmonic signals sequentially starting from a lowest frequency to a highest frequency; and performing the time-frequency transformation with respect to the amplitudes of the harmonic signals by referring to the numbering of the harmonic signals as frame numbers of the signal in the time domain.

3. The method of claim 1 , wherein the encoding the time-frequency transformed values comprises: selecting a predetermined number of values from among the time-frequency transformed values from a low frequency region; and encoding the selected predetermined number of values.

4. The method of claim 1 , wherein the time-frequency transformation operation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

5. The method of claim 1 , wherein the harmonic parameters comprise frequency, amplitude, and phase of the harmonic signals.

6. The method of claim 1 , wherein the harmonic parameters comprise an amplitude of a sinusoidal signal having a frequency with a predetermined correction value for a multiple frequency of a fundamental frequency signal.

7. An apparatus for encoding an audio signal, the apparatus comprising: a harmonic analyzing unit, which performs a harmonic analysis with respect to an input signal and determines harmonic parameters with respect to harmonic signals, wherein the harmonic parameters comprises amplitudes of the harmonic signals; a time-frequency transforming unit, which performs a time-frequency transformation by correlating the amplitudes of the harmonic signals included in the harmonic parameters to signals in a time domain instead of signals in a frequency domain, and applies a time-frequency transformation operation to the amplitudes in the time domain to generate time-frequency transformed values in the frequency domain; and a transformed value encoding unit which encodes the time-frequency transformed values.

8. The apparatus of claim 7 , wherein the time-frequency transforming unit numbers the harmonic signals sequentially starting from a lowest frequency to a highest frequency, and performs a time-frequency transformation by referring to the numbers of the harmonic signals as frame numbers of the signal in the time domain.

9. The apparatus of claim 7 , wherein the transformed value encoding unit selects a predetermined number of values from among the time-frequency transformed values from a low frequency region and encodes the selected predetermined number of values.

10. The apparatus of claim 7 , wherein the time-frequency transformation operation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

11. The apparatus of claim 7 , wherein the harmonic parameters comprise frequency, amplitude, and phase of the harmonic signals.

12. The apparatus of claim 7 , wherein the harmonic parameters comprise an amplitude of a sinusoidal signal having a frequency with a predetermined correction value for a multiple frequency of a fundamental frequency signal.

13. A computer readable recording medium having embodied thereon a computer program for executing a method comprising: performing harmonic analysis with respect to an input signal to determine harmonic parameters with respect to harmonic signals, wherein the harmonic parameters comprises amplitudes of the harmonic signals; performing a time-frequency transformation by correlating the amplitudes of the harmonic signals included in the harmonic parameters to signals in a time domain instead of signals in a frequency domain, and applying a time-frequency transformation operation to the amplitudes in the time domain to generate time-frequency transformed values in the frequency domain; and encoding the time-frequency transformed values.

14. A method of decoding an audio signal, the method comprising: decoding encoded data to determine time-frequency transformed values in a frequency domain; applying an inverse time-frequency transformation operation to the time-frequency transformed values so as to determine amplitudes of harmonic signals in a time domain; and determining the amplitudes of the harmonic signals in the frequency domain by correlating the harmonic signals in the time domain as harmonic signals in the frequency domain.

15. The method of claim 14 , wherein the determining the amplitudes of the harmonic signals in the frequency domain comprises: sequentially numbering the harmonic signals in the time domain; and determining a value, obtained by multiplying a fundamental frequency by a number of the numbered harmonic signals, as a frequency of the harmonic signal that corresponds to the amplitudes in the frequency domain.

16. The method of claim 14 , wherein the inverse time-frequency transformation operation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

17. An apparatus for decoding an audio signal, the apparatus comprising: a decoding unit, which decodes encoded data and determines time-frequency transformed values in a frequency domain; a time-frequency inverse-transforming unit, which applies an inverse time-frequency transformation operation to the time-frequency transformed values so as to determine amplitudes of harmonic signals in a time domain; and a frequency region signal regarding unit, which determines the amplitudes of the harmonic signals in the frequency domain by correlating the harmonic signals in the time domain as harmonic signals in the frequency domain.

18. The apparatus of claim 17 , wherein the frequency region signal regarding unit sequentially numbers the harmonic signals in the time domain, and determines a value, obtained by multiplying a fundamental frequency by a number of the numbered harmonic signals, as a frequency of the harmonic signal that corresponds to the amplitudes in the frequency domain.

19. The apparatus of claim 17 , wherein the inverse time-frequency transformation operation is one of Discrete Cosine Transformation (DCT), Modified Discrete Cosine Transformation (MDCT), and Fast Fourier Transformation (FFT).

20. A computer readable recording medium having embodied thereon a computer program for executing a method comprising: decoding encoded data to determine time-frequency transformed values in a frequency domain; applying an inverse time-frequency transformation operation to the time-frequency transformed values so as to determine amplitudes of harmonic signals in a time domain; and determining the amplitudes of the harmonic signals in the frequency domain by correlating the harmonic signals in the time domain as harmonic signals in the frequency domain.